Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

371
FXUS63 KLOT 092347
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
547 PM CST Fri Jan 9 2026

.KEY MESSAGES...

- Another storm system will deliver a round of snow and rain,
  blustery winds, and falling temperatures Saturday through
  Sunday morning. Some wet/slushy snow accumulations are
  expected Saturday morning, predominantly north of I-80.

- Monitoring a threat for robust, wind-whipped snow showers
  Saturday evening which may lead to quick snow accumulations
  and sharply-reduced visibilities.

- Up and then down temperatures next week with occasional
  opportunities for (mainly light) precipitation.

&&

.DISCUSSION...
Issued at 215 PM CST Fri Jan 9 2026

Through Saturday Night:

Areas of low stratus will persist across the region this
afternoon, and any clearing that occurs this evening will
likely be fairly short-lived as warm advection increases in
advance of our next weather-maker. This disturbance--a vigorous
shortwave spinning across SW Kansas and the Oklahoma/Texas
Panhandles--will eject northeastward across the central CONUS
this evening and overnight. At the same time, interaction with a
synoptic scale trough/upper low scooting across North Dakota
and the Minnesota Arrowhead will take place which will
eventually lead to cyclogenesis and a deepening surface low as
these features pass overhead on Saturday.

In advance of all of this, moisture is forecast to increase this
evening and overnight, which will manifest as a rapid expansion
of low cloud cover and eventually drizzle/light showers. With
some degree of ongoing clearing, temperatures may end up
meandering down into the mid low/mid 30s this evening. However,
with dewpoints currently in the mid and upper 30s and no notable
advection of drier air, don`t currently have significant
concerns of prolonged sub-freezing temperatures causing initial
icing issues with air temperatures largely expected to settle
just above freezing.

Large scale forcing will increase rapidly very late
tonight/early Saturday morning. This will drive a rapid
expansion of precipitation, initially mainly north and west of
I-55. As deeper saturation arrives, precipitation in this area
should transition quickly to snow through about 5-7 AM. Forecast
soundings indicate a brief window (2-3 hours or so) early
Saturday morning with fairly robust ascent coinciding with the
DGZ in addition to ephemeral pockets of near-upright
instability. In addition to at least modest 850-700 mb fgen,
this may facilitate a brief period of boosted precip rates
through late Saturday morning. Surface air and wetbulb
temperatures are generally expected to be at or just a hair
above freezing during this period, which should largely limit
snowfall accumulations to grassy and elevated, untreated
surfaces, but envision there may be some SW-NE oriented
transient banding with rates that may briefly get high enough to
result in some slushy accums on some road surfaces across parts
of interior northern Illinois. Based on the latest guidance,
have slightly increased snowfall amounts along and north of I-88
and west of about I-355/94 (locally up to 2 inches), but again
most of this likely won`t accumulate on the heavily-traveled
thoroughfares.

To the south and east of I-55, slightly warmer surface temps
and a rapidly-arriving mid-level dryslot suggest any transition
to snow won`t amount to much before precipitation ends from SW
to NE through midday and early afternoon. Isolated to scattered
rain/snow showers will be possible through the afternoon, but
other than briefly knocking down visibilities, no significant
impacts are expected.

This may change a bit by early Saturday evening as a subtle
surface trough axis pushes southeast out of Iowa and Wisconsin
ahead of a robust 700-500 mb vort lobe. Air temperatures will be
falling quickly into the 20s during this period, and forecast
soundings indicate a quick increase in boundary layer lapse
rates and moisture. Have increased PoPs a bit Saturday evening,
with a mention of scattered snow showers across pretty much all
of the forecast area. Not currently to the level of a
significant snow squall set up, but quick coatings with wind-
whipped snow showers appears to be on the table, mainly during
the 6 PM Saturday to 1 AM Sunday timeframe. With some forecast
guidance (extended RAP for example) developing upwards of 50-75
J/kg of near-surface CAPE (which might be a bit overdone), can`t
rule out the potential for some true squall-like action in
spots, so something we`ll keep a close eye on.

Snow showers may persist through the rest of the night, but the
boundary layer is forecast to dry out with time. Intermittent
lake effect snow showers may continue into early Sunday morning,
mainly across parts of Porter County.

Carlaw


Sunday through Friday:

Anomalously strong mid-upper ridging will establish near the
Pacific Coast through next week, resulting in a predominantly
northwesterly flow pattern for the eastern 2/3 of North America.
Seasonable conditions on Sunday will give way to a few days of
solidly above normal temps (through Tuesday night), followed by a
return to more seasonable readings for the rest of the week. There
will be occasional opportunities for precipitation, though the
deep northwest flow pattern will be unfavorable for any moisture
laden systems.

Sensible weather wise, blustery conditions through around midday
Sunday (gusts to 30-35 mph) will result in wind chills in the
single digits and teens. With little if any snow cover and
increasing sunshine favored in the afternoon, highs should recover
to near 30F to the lower 30s, near to even slightly above normal
for the date (albeit with relatively chilly wind chills). The
winds will diminish through the afternoon and into the evening as
1035 mb high pressure passes to our south and settles towards the
Ohio Valley. Following an evening dip in temps (upper teens to mid
20s), the surface high will sink farther south, with a commensurate
increase in west-southwest winds resulting in rising temps
overnight.

With the first in a series of clipper-type systems passing well to
the north Monday into Tuesday, the breezy warm advection regime
will result in highs in the upper 30s to lower 40s Monday, mostly
above freezing lows Monday night, and then highs well into the 40s
on Tuesday. Some rain showers are possible Tuesday afternoon and
evening with the cold front trailing from low pressure passing
through or just north of the northern Great Lakes.

Mid-upper troughing will deepen over the eastern US on Wednesday
as a few embedded short-wave impulses press southeastward. The
cold advection regime on Wednesday should support at least
scattered snow showers (30-40% PoPs for now are reasonable),
though marginal surface temps to start the day and showery nature
of the snow should tend to limit accumulation/impact potential.
We`ll then need to watch for a window of favorable lake effect
thermodynamics Wednesday night into Thursday morning, supporting
(~30-40%) chance PoPs for portions of northeast IL and
northwest IN. There should be a brief break in the wake of
however potential lake effect snow shower activity plays out,
with signs pointing toward an additional clipper system or two
affecting the region sometime in the Friday-Saturday timeframe.

Castro

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 547 PM CST Fri Jan 9 2026

Forecast concerns include...

Mvfr cigs through the period.
A period of snow Saturday morning.
Snow showers late Saturday afternoon/evening.
Strong/gusty west/northwest winds Saturday afternoon/night.

The edge of mvfr cigs have stalled from a SQI/DKB/PWK line early
this evening and as high pressure moves across the area and
winds eventually turn easterly this evening and southeast later
tonight, its possible these mvfr cigs will continue and included
that for the Chicago terminals. Mvfr cigs will return to RFD
tonight, but quite a bit of uncertainty this evening. While some
scattering is possible Saturday, mainly prevailing mvfr cigs
look to continue through the period.

A quick moving system will move across the area Saturday morning
bringing primarily a band of light/moderate snow to parts of
northern IL. This precipitation may start or mix with rain, then
change to all snow, especially along and north of a C09/LOT/MDW
line. Lowered visibility to 1sm in the tempo, 3/4sm at RFD, but
its possible that these lower visibilities may become prevailing
for a 2-3 hour window. With temperatures near freezing, there
may be some further vis reduction due to mist/light fog, thus
some 1/2sm vis is also possible. Ifr cigs will also be possible
during this time period.

Scattered snow showers will be possible late Saturday afternoon
into Saturday evening. Some of these snow showers will likely
produce brief periods of moderate snow that may reduce
visibility less than 1sm. Current prob mention has this
potential handled well for now.

Light easterly or light and variable winds this evening will
become light southeast tonight, then shift westerly once the
snow begins Saturday morning. As the snow ends, winds will turn
to the west/northwest with speeds/gusts increasing. Gusts into
the mid 20kt range can be expected Saturday afternoon into
Saturday night with gusts possibly increasing to 30kt late
Saturday evening. This may cause some blowing snow with any of
the snow showers Saturday evening. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 1 PM Saturday to 3 PM CST Sunday for
     Winthrop Harbor IL to Gary IN.

     Small Craft Advisory from 1 PM Saturday to midnight CST Sunday
     night for Gary to Burns Harbor IN-Burns Harbor to
     Michigan City IN.

&&

$$

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